Skip to main content

Full text of "Alaskan glacier studies of the National Geographic Society in the Yakutat Bay, Prince William Sound and lower Copper River regions"

See other formats

Petroff intimates l that some of the early Russian accounts to which he had access, suggested a tidal glacier in Port Fidalgo, and in one place he speaks of the "tremendous glaciers " in Port Fidalgo. As he seems to have made a mistake with regard to the Valdez Glacier being tidal at the same time and Columbia Bay having no tidal glacier, it is quite possible that he is in error about the fiord in which these glaciers were located.
In May, 1898, Port Fidalgo was explored by F. C. Schrader 2 who found no tidewater glaciers, but reported that "the shore is mountainous throughout, some of the mountains rising to a height of 4000 feet, into a region of perpetual snow and glaciers, especially on the north and east. Two mountain streams of considerable size, and apparently of glacial origin enter the inlet near the head—one from the north and one from the east. They have done much toward silting up the inlet, and flow over extensive deltoid deposits of gravel and mud flats at their mouths, especially at low tide." In this year Emil Mahlo made a rough contour map of Port Fidalgo, without mapping any of the glaciers.
The U. S. Coast and Geodetic Survey parties 8 in 1901 and 1908 mapped a small ice mass on the slopes of Mt. Denson. Grant and Higgins made a geological map of Port Fidalgo in 1908,4 showing one small non-tidal ice tongue near the head of the fiord. Excepting at Goose Island our own knowledge of Port Fidalgo, as well as the fiords of Port Gravina, and Sheep and Simpson Bays at the south, are based entirely upon observations from the steamers and from launch trips past the mouths of these indentations.
Glaciation Above Sea Level. The fiord walls above sea level suggest the same profound glacial erosion observed in the parts of Prince William Sound already described. There are cirques in the mountains and the fiord walls are rounded and smoothed. Bligh Island (1634 feet high), north of the entrance of Port Fidalgo, has the rounded form that shows it was completely overridden by ice. On the eastern side of Tatitlek Narrows, near Ellamer, the height of glaciation determined by Grant5 and Capps fl was 2800 to 3000 feet. Goose Island (320 feet high), south of the entrance of Port Fidalgo, has the rounded form resulting from complete overriding by the glacier. The steepened slope of Knowles Head, between Ports Fidalgo and Gravina, is interpreted as the result of glacial erosion rather than of wave work, which does not at present reach its base, the prominent yellowish landslide upon its face being an indirect recent result of glacial oversteep-ening.
Submarine Form of Fiord Through Glaciation. Below sea level the soundings also indicate extensive glacial erosion. No soundings have been made in the eastern half of Port Fidalgo beyond Fish Bay; but from this point westward to Prince William Sound the detailed soundings by the Coast Survey 7 show that the outer part of the fiord has a depth of 542 to 714 feet, with a slight westward upgrade in the broad outer part where glacial erosion was less effective because the fiord walls are farther apart. The cross-
• Petroff, Ivan, Population, Industries and Resources of Alaska, Tenth Census of the United States, 1880, Vol. Vm, 1884, p. 27.
i Schrader, F. C., A Reconnaissance of a Part of Prince William Sound, and the Copper River District, Alaska, in 1898, 20th Ann. Rept., U. S. Geol. Survey, Part VIE, 1900, pp. 854 and 380.
• U. S. Coast and Geod. Survey, Chart 8519, 1907.
< Grant, U. S. and Higgins, D. F., Bull. 443, U. S, Geol. Survey, 1910, PI. I, facing p. 10, PI. H, in pocket.
• Op. cit., p. 19.
• Capps, S. R. and Johnson, B. L., Bull. 542, U. S. Geol. Survey, 1913, p. 89. ' U. S. Coast and^Geod. Survey, Charts 8519 and 8550.